Bernie Masters is a geologist/zoologist who spent 8 years as a member of the Western Australian Parliament. Married to Carolina since 1976 and living in south west WA, Bernie is involved in many community groups. This blog offers insights into politics, the environment and other issues that annoy or interest him. For something completely different, visit www.fiatechnology.com.au for information about vegetated floating islands - the natural way to improve water quality.

Wednesday, November 30, 2016

With Climate Change, Not All Wildlife Population Shifts Are Predictable

AMHERST,
Mass. – Wildlife ecologists who study the effects of climate change
assume, with support from several studies, that warming temperatures
caused by climate change are forcing animals to move either northward or
upslope on mountainsides to stay within their natural climate
conditions.

But a new study of lowland and higher-mountain bird species by
wildlife ecologists Bill DeLuca and David King at the University of
Massachusetts Amherst now reports an unexpected and “unprecedented”
inconsistency in such shifts. The majority of the mountain bird
community responded against expectation and shifted downslope despite
warming trends in the mountains. They say the result “highlights the
need for caution when applying conventional expectations to species’
responses to climate change.”

In their article in the current issue of Journal of Ornithology,
DeLuca and King say that although other studies have found species
shifting either downslope or toward the equator, the opposite of
expectations given the warming climate, theirs is the first to find that
the majority of the bird community is responding contrary to these
expectations.

DeLuca says of the unexpected shift among many bird species, “This is
really important information for mountains in the northeastern U.S.
like the White Mountains, Green Mountains and the Adirondacks. It helps
to confirm that human activities like climate change, pollution and land
management are affecting the distribution of mountain species.”

Species shifts up and down mountainsides have been documented around
the world but this is the first time that recent elevational shifts of
birds have been found in the northeastern United States, they add. It
should be noted that in this study, the lowland bird community shifted
upslope over the 17-year study period, consistent with expectations
given recent warming in the region.

The researchers analyzed 28 bird species including yellow-bellied
flycatcher, white-throated sparrow, winter wren, Swainson’s thrush,
Nashville warbler, yellow-rumped warbler and dark-eyed junco and
measured the elevations of their distribution along 42 mountainsides in
the White Mountains of New Hampshire from 1993 to 2009.

The authors report that as predicted, the upper elevation boundary of
nine out of 16 lowland species showed evidence of shifting upslope an
average of 99 meters [about 325 feet] over the study period. But, they
add, “contrary to our expectations, nine out of 11 mountain birds
shifted their lower boundaries downslope an average of 19 meters [about
62 feet] over the 17-year study period.”
A possible explanation for the observation might be changes in forest
composition, DeLuca and King suggest. For example, red spruce and paper
birch have declined (due in part to acid rain) in the ecotone, the
transition between the lower elevation deciduous forest and the higher
elevation coniferous forest, and “the void left by the decline of spruce
and birch has, in part, been filled by balsam fir.” Further, “all of
the high-elevation species we found to be shifting downslope are closely
associated with balsam fir,” meaning these birds may be following
suitable habitat.

The warming climate at mid elevations might be driving the march of
lowland elevations upslope they say. Based on work from the Mount
Washington Observatory, the mid elevations around Mount Washington are
warming. “If lowland species are limited by cooler temperatures, this
mid-elevation warming might enable them to follow the warmer temps
upslope” explains DeLuca.

For this work, trained observers from the White Mountain National
Forest surveyed birds using five-minute point counts at fixed survey
locations between 740 meters (about 2,440 feet) and 1470 m (4,800 ft.)
annually from 1993 to 2000, then in 2003, 2005, 2007, and 2009. For a
point count, all birds seen or heard are recorded as being either less
than or greater than 50 meters from the observer. Surveys were conducted
once per year during the breeding season in June. The observers
surveyed a total of 768 locations on 42 separate transects along hiking
trails.

Overall, 82 percent, or nine of the 11 high elevation species
analyzed showed evidence of shifting downslope, while 10 of 16 or 63
percent of lowland species showed evidence of shifting upslope.

This work was supported by the White Mountain National Forest and the U.S. Forest Service Northern Research Station.